1. Field of the Invention
This invention relates to a method and system for transmitting audio signals over a dedicated video signal line, and particularly relates to a simple and inexpensive method and system for transmitting analog audio signals over a dedicated video line within the normal video area of the NTSC or PAL/SECAM signal.
2. Description of the Prior Art
Methods and systems for transmitting audio signals over dedicated video signal lines are in existence. However, presently existing systems use parallel (additional) audio channel or a digital technique to transmit digital audio signals within the various synchronizing signals of the video picture signal. As examples, the invention of U.S. Pat. No. 5,842,171 teaches the encoding of digital audio into a SMPTE digitized video signal as a burst of digital data that fits into a specified time slot of the SMPTE standard. The invention of U.S. Pat. No. 5,929,922 teaches the sending of digital audio inside television vertical blanking intervals. The invention of U.S. Pat. No. 5,940,070 refers to a method of sending digitized audio over one of the video lines of a standard VGA display system, with synchronization data coming over a separate line. Each of these systems requires digital-to-analog (DTA) converters and analog-to-digital (ATD) converters in order to convert the particular audio signal into a useable format, and one requires an additional transmission line. In addition, while inserting additional information into the video signals during the video blanking periods is well known, this technique typically violates the TV video signal standard, frequently resulting in visible retraces on the video screen.
It is therefore desirable to provide a simple method and apparatus for sending audio signals along a line dedicated to video without the need for either a separate communication line, or the need for cumbersome DTA/ATD converters and buffering systems at either end of the line.